Cohesive energy density - Cohesive energy density

The energy required to separate molecules or atoms in a cohesive state such as a solid or liquid to infinity is called cohesive energy, and its division by volume is called cohesive energy density (CED). CED, along with internal pressure, is used as a measure of the strength of interactions between molecules. Comparing the CED of ionic crystals and molecular crystals, the ionic bonding force of the former is stronger than the van der Waals force of the latter, and the CED of ionic crystals is generally larger. The larger the CED of a molecule, the higher the melting point. The CED of a liquid changes depending on the temperature, but is on the order of several tens to several hundreds of J cm ^-3 , and the CED of low molecular weight substances and high molecular weight substances is not very different. Since the heat of fusion is much smaller than the heat of vaporization, the cohesive energy is approximately equal to the heat of vaporization. The CED of low molecular weight substances can be calculated using this method, but in the case of high molecular weight substances, they cannot become gases, so it must be calculated using a different method. The polymer substance is swelled with a low molecular weight liquid, the solubility parameter δ is calculated, and

δ =
The CED of polymeric substances has been obtained from the above.

Source: Morikita Publishing "Chemical Dictionary (2nd Edition)" Information about the Chemical Dictionary 2nd Edition

固体や液体などの凝集状態にある分子，原子を無限遠にまで引き離すのに必要なエネルギーを凝集エネルギーといい，それを体積で割ったものを凝集エネルギー密度(CED)という．CEDは内部圧とともに分子間の相互作用の強さを表す尺度として用いられている．イオン結晶，分子性結晶のCEDを比べてみると，前者のイオン結合力は後者のファンデルワールス力よりは強く，一般にCEDはイオン結晶のほうが大きい．CEDが大きい分子ほど融点が高い．液体のCEDは温度によって変化するが，数十～数百 J cm^－3 程度であり，低分子物質と高分子物質のCEDはあまり違わない．融解熱は蒸発熱に比べてかなり小さいから，近似的に凝集エネルギーは蒸発熱に等しい．低分子物質のCEDはこの方法で求められるが，高分子物質の場合は気体になりえないので，ほかの方法で求めなければならない．低分子液体で高分子物質を膨潤させ，溶解度パラメーターδを求め，

δ＝
から，高分子物質のCEDが得られている．

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